Method of press molding glass optical elements

ABSTRACT

A method of press-molding glass optical elements by press-molding glass, having a high melting point, at a temperature of 650° C. and higher using a die for press-molding glass optical elements which includes a base material having a heat resistance and sufficient strength to withstand press-molding of optical glass elements, a cutting layer on the base material, and a surface protective layer on the cutting layer. The cutting layer is formed of an alloy film containing P and one metal selected from the group Ni, Co, and Fe, and one metal from the group Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, or an alloy film containing Cu and 20 to 80 atom % of one metal selected from the group Ni, Co, Fe, Si, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, or an alloy film containing Si and 20 to 80 atom % of one metal selected from the group Ni, Co, Fe, Cu, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir. The surface protective layer is formed of an alloy film of at least one metal selected from the group Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta.

This application is a division of application Ser. No. 08/623,889, filedMar. 29, 1996, which is a division of application Ser. No. 08/281,690,filed Jul. 28, 1994, both pending.

FIELD OF INVENTION

This invention relates to glass optical elements, and in particular, toa method for press-molding glass optical elements having high surfaceaccuracy. This invention also relates to a die used for thepress-molding process, and to a method of manufacturing the die.

BACKGROUND OF THE INVENTION

In order to press-mold glass optical elements having high accuracyrepeatedly by means of a die, it is necessary to use a die materialwhich is stable at high temperatures, has excellent resistance tooxidation, and is inert with respect to glass. In addition, the materialmust have excellent mechanical strength so that the surface accuracy ismaintained when pressed. On the other hand, the material must haveexcellent machinability so as to be machined precisely and easily.

It is disclosed that die materials which meet these requirements to somedegree are a mixed material consisting of titanium carbide (TiC) andmetal (Laid-open Japanese patent application No. (Tokkai Sho) 59-121126)or a material comprising a base material of cemented carbide on which aprecious metal film is formed (Laid-open Japanese patent applicationNo.(Tokkai Sho) 62-96331).

However, the conventional materials of the die do not meet theabove-mentioned requirements completely. For example, the material ofthe die using a mixed material of TiC and metal has excellent mechanicalstrength, but is poor in machinability due to its extreme hardness.Thus, it is difficult to machine with high accuracy. In addition, thismaterial has a further defect in that it easily reacts to lead (Pb) oran alkaline element contained in glass optical elements When a materialcomprises a base material of cemented carbide on which a precious metalfilm is formed, a diamond wheel is used to machine the cemented carbide.At this time, it is difficult to form a fine shape due to wear of thediamond wheel. Therefore, a special processing device is needed.Furthermore, there are problems that the process take a long time andthat the die is extremely expensive.

A further problem is that a diamond tool used for cutting the hard basematerial is worn down during the process. Therefore, it is impossible toproceed with the cutting, and a shape having a small radius of curvaturewhich can not be attained by a grinding process can not be fabricated.

The following method of manufacturing a die has proposed a solution tothe above-noted problems (Laid-open Japanese patent applicationNo.(Tokkai Sho) 62-3031). A base material used here has excellent heatresistance, heat shock resistance, and strength at high temperatures. Afine cutting layer comprising a material which can be ground and cutexcellently and is chemically stable and having a high melting point,for example, Pt-alloy film, is formed on the base material. After thislayer is formed into a desired surface through a fine machining process,the mold surface is coated with a Pt-alloy film for protection.

Another method of manufacturing a die is disclosed in Laid-open Japanesepatent application No.(Tokkai Hei) 3-23230. In this instance, a filmformed on a base material of cemented carbide has good adhesion to thebase material. On top of this, an electroless Ni-P plated film, forexample, is formed as a fine cutting layer. After this layer is cutprecisely into a desired surface, the mold surface is coated with analloy film for protection.

However, using the above-noted manufacturing methods, the film formed asa cutting layer did not have sufficient strength so that the die wasdeformed when press-molded. Therefore, it was actually impossible tomold at high temperatures of 650° C. and higher.

SUMMARY OF THE INVENTION

It is an object of this invention to solve the above-noted problems byproviding a die for press-molding glass optical elements having highmelting points and various shapes repeatedly. This was not possible withconventional grinding methods.

In order to accomplish these and other objects and advantages, a die forpress-molding glass optical elements in the invention comprises a basematerial having heat resistance and sufficient strength to withstand thepress-molding process of glass optical elements, and a cutting layerformed on said base material comprising at least one film selected fromthe group consisting of an alloy film containing phosphorus (P), analloy film containing boron (B), an alloy film containing copper (Cu),an alloy film containing silicon (Si), and an amorphous film. Thecutting layer is covered with an alloy film which includes at least onemetal selected from the group consisting of Pt, palladium (Pd), iridium(Ir), rhodium (Rh), osmium (Os), ruthenium (Ru), rhenium (Re), tungsten(W), and tantalum (Ta).

It is preferable in this embodiment that an intermediate layercomprising at least one film selected from the group consisting ofmetal, carbide, nitrogen, and oxide is present between the base materialand the cutting layer.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing P is present, the alloy film also contains one metalselected from the group consisting of Ni, Co, and Fe, and furthercontains one metal selected from the group consisting of Si, titanium(Ti), Cu, zirconium (Zr), niobium (Nb), molybdenum (Mo), Ru, Rh, Pd,hafnium (Hf), Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing B is present, the alloy film also contains one metalselected from the group consisting of Ni, Co, and Fe, and furthercontains one metal selected from the group consisting of Si, Ti, Cu, Zr,Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that the alloy filmcontaining Cu be a Cu-alloy film containing 20 to 80% by atom(hereinafter abbreviated as at %) of one metal selected from the groupconsisting of Ni, Co, Fe, Si, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re,Os, and Ir.

Furthermore, it is preferable in this embodiment that the alloy filmcontaining Si be a Si-alloy film containing 20 to 80 at % of one metalselected from the group consisting of Ni, Co, Fe, Cu, Ti, Zr, Nb, Mo,Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

It is preferable in this embodiment that when the amorphous film ispresent, it comprises at least one metal selected from or one alloyconsisting of the group consisting of Ni, Co, Cr, Ta, Mo, Ti, W, Nb,vanadium (V), Cu, and alumium (Al).

The method of manufacturing a die for press-molding in a secondembodiment of this invention comprises forming a base material havingheat resistance and sufficient strength to withstand the press-moldingprocess of glass optical elements into a shape similar to a desiredshape of the die, forming a cutting layer on said base materialcomprising at least one film selected from the group consisting of analloy film containing P, an alloy film containing B, an alloy filmcontaining Cu, an alloy film containing Si, and an amorphous film bymeans of at least one method selected from the group consisting of aplating method, an evaporation method, a sputtering method, and an ionplating method, and covering the cutting layer with an alloy film whichincludes at least one metal selected from the group consisting of Pt,Pd, Ir, Rh, Os, Ru, Re, W, and Ta.

It is preferable that this embodiment further comprises forming anintermediate layer comprising at least one film selected from the groupconsisting of metal, carbide, nitrogen, and oxide between the basematerial and the cutting layer by means of at least one method selectedfrom the group consisting of a plating method, an evaporation method, asputtering method, an ion plating method, and a chemical vapordeposition (CVD) method.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing P is present, the film further comprises one metalselected from the group consisting of Ni, Co, and Fe, and one metalselected from the group consisting of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh,Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing B is present, the film further comprises a metalselected from the group consisting of Ni, Co, and Fe, and also comprisesone metal selected from the group consisting of Si, Ti, Cu, Zr, Nb, Mo,Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing Cu is present, it is a Cu-alloy film containing 20 to 80at % of a metal selected from the group consisting of Ni, Co, Fe, Si,Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing Si is present, it is a Si-alloy film containing 20 to 80at % of a metal selected from the group consisting of Ni, Co, Fe, Cu,Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the amorphousfilm is present, it is at least one metal selected from or one alloyconsisting of the group consisting of Ni, Co, Cr, Ta, Mo, Ti, W, Nb, V,Cu, and Al.

A method of press-molding glass optical elements with a die in a thirdembodiment of the invention comprises press-molding glass having a highmelting point at a temperature of 650° C. and higher by using a die forpress-molding glass optical elements which comprises a base materialhaving heat resistance and sufficient strength to withstand thepress-molding process of glass optical elements, a cutting layer on saidbase material comprising at least one film selected from the groupconsisting of an alloy film containing P, an alloy film containing B, analloy film containing Cu, an alloy film containing Si, and an amorphousfilm, wherein the cutting layer is covered with an alloy film whichincludes at least one metal selected from the group consisting of Pt,Pd, Ir, Rh, Os, Ru, Re, W, and Ta.

It is preferable in this embodiment that when the alloy film containingP is present, it also comprises a metal selected from the groupconsisting of Ni, Co, and Fe, and further comprises a metal selectedfrom the group consisting of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta,W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that when the alloyfilm containing B is present, it also comprises a metal selected fromthe group consisting of Ni, Co, and Fe, and further comprises one metalselected from the group consisting of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh,Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that the alloy filmcontaining Cu is a Cu-alloy film containing 20 to 80 at % of a metalselected from the group consisting of Ni, Co, Fe, Si, Ti, Zr, Nb, Mo,Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that the alloy filmcontaining Si is a Si-alloy film containing 20 to 80 at % of a metalselected from the group consisting of Ni, Co, Fe, Cu, Ti, Zr, Nb, Mo,Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir.

Furthermore, it is preferable in this embodiment that the amorphous filmis at least one metal selected from or one alloy consisting of from thegroup consisting of Ni, Co, Cr, Ta, Mo, Ti, W, Nb, V, Cu, and Al.

In particular, this die comprises a base material having heat resistanceand sufficient strength to withstand a press-molding process for opticalglass, and a cutting layer formed on said base material comprising aternary alloy film consisting of one metal selected from the groupconsisting of Ni, Co, and Fe, one metal selected from the groupconsisting of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, andIr, and one element selected from the group consisting of P and B, or aCu-alloy film containing 20 to 80 at % of one metal selected from thegroup consisting of Ni, Co, Fe, Si, Ti, Zr, Nb, Mo, Ru, Rh, Pb, Hf, Ta,W, Re, Os, and Ir, or a Si-alloy film containing 20 to 80 at % of onemetal selected from the group consisting of Cu, Ni, Co, Fe, Ti, Zr, Nb,Mo, Ru, Rh, Pb, Hf, Ta, W, Re, Os, and Ir, or an amorphous filmcomprising at least one metal selected from the group consisting of Ni,Co, Cr, Ta, Mo, Ti, W, Nb, V, Cu, and Al. After this cutting layer iscut with high surface accuracy, an alloy film containing at least onemetal selected from the group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re,W, and Ta is formed as a protective film on the cutting layer. In thisway, a die is provided which can be used to press-mold glass opticalelements having high melting points and various shapes. By press-moldingan optical glass having a high melting point at the temperature of 65020C. and higher repeatedly, a large quantity of glass optical elementshaving high melting points and various shapes at a low cost can beproduced which was impossible using conventional methods.

Furthermore, by forming an intermediate layer between the base materialand the cutting layer comprising at least one film made from a materialselected from the group consisting of metal, carbide, nitrogen, andoxide, it is possible to prevent the cutting layer from peeling, and itimproves the durability of the die.

A die for press-molding glass optical elements which is manufacturedaccording to the above-noted method, has sufficient strength towithstand the press-molding process by using a base material havingexcellent heat resistance and strength. This invention enables the dieto be cut into a desired shape easily with high accuracy by forming acutting layer which comprises a ternary alloy film comprising a metalselected from the group consisting of Ni, Co, and Fe, one metal selectedfrom the group consisting of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta,W, Re, Os, and Ir, and one element selected from the group consisting ofP and B, or a Cu-alloy film containing 20 to 80 at % of a metal selectedfrom the group consisting of Ni, Co, Fe, Si, Ti, Zr, Nb, Mo, Ru, Rh, Pb,Hf, Ta, W, Re, Os, and Ir, or a Si-alloy film containing 20 to 80 at %of one metal selected from the group consisting of Cu, Ni, Co, Fe, Ti,Zr, Nb, Mo, Ru, Rh, Pb, Hf, Ta, W, Re, Os, and Ir, or an amorphous filmcomprising at least one metal selected from the group consisting of Ni,Co, Cr, Ta, Mo, Ti, W, Nb, V, Cu, and Al. In addition, this die alsoattains the heat resistance and the strength at high temperatures whichcan stand the press-molding process of glass having a high melting pointat a temperature of 650° C. and higher.

The die also prevents itself from welding with the glass by forming analloy film containing at least one metal selected from the groupconsisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta as a surfaceprotective film.

As a result, this invention enables production of a press-molding diefor glass having a high melting point and various shapes. Bypress-molding the glass using the die of this invention, it enablesproduction of a large quantity of glass optical elements having highmelting points and various shapes at a low cost which was impossible bythe conventional grinding process. Furthermore, by forming anintermediate layer comprising at least one film made of a materialselected from the group consisting of metal, carbide, nitrogen, andoxide, the adhesive strength between the base material and the cuttinglayer improves, and this prevents the film from peeling. Thus, itenables improved durability of the die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of this inventionshowing a die for press-molding glass optical elements.

FIG. 2 is an outline view of a press-molding machine used in oneembodiment of this invention.

FIG. 3 is a cross-sectional view of one embodiment of this inventionshowing a die for press-molding glass optical elements.

FIG. 4 is a cross-sectional view of one embodiment of this inventionshowing a die for press-molding glass optical elements.

FIG. 5 is a cross-sectional view of one embodiment of this inventionshowing a die for press-molding glass optical elements.

FIG. 6 is a cross-sectional view of one embodiment of this inventionshowing a die for press-molding glass optical elements.

FIG. 7 is a cross-sectional view of one embodiment of this inventionshowing a press-molding die for glass optical elements.

DETAILED DESCRIPTION OF THE INVENTION

This invention is specifically described by referring to the followingillustrative examples and attached figures.

EXAMPLE 1

A molding die of this embodiment is shown in FIG. 1. As shown in FIG. 1,the molding die of this embodiment comprises a base material of cementedcarbide 13 on top of which a cutting layer 12 is formed into a desiredshape with high accuracy. Furthermore, a Pt-Ir alloy protective layer 11is formed on cutting layer 12 for protection.

A manufacturing method of the molding die shown in FIG. 1 is describedas follows.

First of all, base material of cemented carbide 13 is processed into theshape similar to the desired shape by means of electrical dischargemachining.

Then, cutting layer 12 is formed by a sputtering method on top of thebase material 13 which is roughly processed by the electrical dischargemachining.

After that, the cutting layer 12 is cut using a diamond tool, formingthe cutting layer 12 into a desired shape with high accuracy.

When this method is explained in detail by providing specific values,base material of cemented carbide 13 is a cemented carbide materialmainly comprising tungsten carbide (WC) of 6 mm diameter and 10 mmthickness which is roughly processed by electrical discharge machininginto upper and lower dies having hollow-shaped press surfaces of 1 mmradius of curvature.

Cutting layer 12 is formed on top of the roughly processed die with athickness of about 15 μm. By cutting precisely the cutting layer 12, ahollow-shaped die of 1 mm radius of curvature was obtained with highaccuracy which was difficult to attain with a conventional grindingprocess. In addition, this method required only 1/10 of the time neededfor a conventional grinding process.

Furthermore, the Pt-Ir alloy protective layer 11 is formed with athickness of 3 μm by the sputtering method.

This embodiment uses a ternary alloy film as the cutting layer 12. Inparticular, it is possible to use Ni-P ternary alloys, for example,Ni-Si-P, Ni-Ti-P, Ni-Cu-P, Ni-Zr-P, Ni-Nb-P, Ni-Mo-P, Ni-Ru-P, Ni-Rh-P,Ni-Pd-P, Ni-Hf-P, Ni-Ta-P, Ni-W-P, Ni-Re-P, Ni-Os-P, and Ni-Ir-P.

It is also possible to use Co-P ternary alloys, for example, Co-Si-P,Co-Ti-P, Co-Cu-P, Co-Zr-P, Co-Nb-P, Co-Mo-P, Co-Ru-P, Co-Rh-P, Co-Pd-P,Co-Hf-P, Co-Ta-P, Co-W-P, Co-Re-P, Co-Os-P, and Co-Ir-P.

Furthermore, Fe-P ternary alloys can also be used, for example, Fe-Si-P,Fe-Ti-P, Fe-Cu-P, Fe-Zr-P, Fe-Nb-P, Fe-Mo-P, Fe-Ru-P, Fe-Rh-P, Fe-Pd-P,Fe-Hf-P, Fe-Ta-P, Fe-W-P, Fe-Re-P, Fe-Os-P, and Fe-Ir-P.

In practice, these alloy films can be used as cutting layer 12 when theyhave about 15 μm thickness.

For example, the following method is taken to form the above-mentionedalloy films as cutting layer 12 on the surface of a roughly processeddie by a sputtering method.

First, a Ni-P or Co-P plated layer (percentage content of P=about 12 wt%) is formed with a thickness of about 0.5 mm by an electroless platingmethod on a Ni chip having a size of 10 mm×10 mm×1 mm. Thus, a Ni-P chipor a Co-P chip is formed.

In order to form a Ni-Si-P alloy film, 40 pieces of the Ni-P chip formedby the above-noted method are arranged equally on top of e.g. a Si disktarget having a diameter of 6 inches. The sputtering method is conductedby using this as the target material to form the Ni-Si-P ternary alloyfilm.

In the same way, by arranging 40 pieces of the above-noted chip equallyon top of disk targets of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W,Re, Os or Ir having a diameter of 6 inches and using them as the targetmaterials for the sputtering process, different kinds of ternary alloyfilms can be formed according to each material of disk target beingused.

In order to form a Fe-P ternary alloy film, Fe₃ P compound chips havingsizes of 10 mm×10 mm×1 mm are arranged equally on top of a disk targetcomprising a material selected from the various materials noted in thisexample above. In the same way, the sputtering method is conducted byusing it as the target material to form different kinds of Fe-P ternaryalloy film.

In order to conduct the press-molding process by using the die of FIG.1, this molding die is disposed in a press-molding machine shown in FIG.2. Referring to FIG. 2, reference numeral 21 denotes a fixing block foran upper die; 22, a heater for the upper die; 23, the upper die; 24, aglass material; 25, a lower die; 26, a heater for the lower die; 27, afixing block for the lower die; 210, a plunger; 211, a positioningsensor; 212, a stopper; 213, a cover.

Then, dense barium crown glass (SK-12) 24 manufactured by SUMITA OPTICALGLASS, INC. which was processed into a spherical shape having a radiusof 1 mm is placed on lower die 25, and upper die 23 is placed on thetop. In this condition, the temperature was raised to 650° C., and thepressure was kept at about 40 kg/cm² in a nitrogen atmosphere for twominutes. After that, the temperature was lowered to 550° C. in thiscondition, and the pressure was then released. After it was cooled toroom temperature, the molded glass lens was taken out, and thepress-molding process of the glass optical element was completed.

After repeating this press-molding process 10,000 times, upper and lowerdies 23, 25 were removed from the press-molding machine, and thecondition of the pressed surfaces were observed with an opticalmicroscope. At the same time, the surface roughness (root mean square(RMS) value, nm) of the pressed surface was measured, and the accuracyof each die was evaluated. The results are shown in Table 1 (a) and (b).In Table 1, "surface condition" refers to the observed results of theoptical microscope. The units for surface roughness used in Table 1 areis all nm.

                  TABLE 1 (a)                                                     ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        2      Ni--Si--P 1.03        1.04    satisfactory                             3      Ni--Ti--P 1.01        1.03    satisfactory                             4      Ni--Cu--P 1.01        1.02    satisfactory                             5      Ni--Zr--P 1.04        1.05    satisfactory                             6      Ni--Nb--P 1.02        1.04    satisfactory                             7      Ni--Mo--P 1.01        1.02    satisfactory                             8      Ni--Ru--P 1.01        1.01    satisfactory                             9      Ni--Rh--P 1.03        1.03    satisfactory                             10     Ni--Pd--P 1.05        1.06    satisfactory                             11     Ni--Hf--P 1.02        1.04    satisfactory                             12     Ni--Ta--P 1.02        1.03    satisfactory                             13     Ni--W--P  1.05        1.06    satisfactory                             14     Ni--Re--P 1.02        1.03    satisfactory                             15     Ni--Os--P 1.01        1.01    satisfactory                             16     Ni--Ir--P 1.02        1.03    satisfactory                             17     Co--Si--P 1.07        1.09    satisfactory                             18     Co--Ti--P 1.05        1.08    satisfactory                             19     Co--Cu--P 1.03        1.03    satisfactory                             20     Co--Zr--P 1.07        1.09    satisfactory                             21     Co--Nb--P 1.07        1.10    satisfactory                             22     Co--Mo--P 1.06        1.09    satisfactory                             23     Co--Ru--P 1.04        1.09    satisfactory                             24     Co--Rh--P 1.07        1.08    satisfactory                             25     Co--Pd--P 1.05        1.06    satisfactory                             26     Co--Hf--P 1.04        1.06    satisfactory                             27     Co--Ta--P 1.01        1.01    satisfactory                             28     Co--W--P  1.04        1.05    satisfactory                             29     Co--Re--P 1.06        1.09    satisfactory                             30     Co--Os--P 1.09        1.11    satisfactory                             31     Co--Ir--P 1.05        1.08    satisfactory                             ______________________________________                                    

                  TABLE 1 (b)                                                     ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        32     Fe--Si--P 1.04        1.05    satisfactory                             33     Fe--Ti--P 1.06        1.07    satisfactory                             34     Fe--Cu--P 1.03        1.06    satisfactory                             35     Fe--Zr--P 1.07        1.09    satisfactory                             36     Fe--Nb--P 1.05        1.06    satisfactory                             37     Fe--Mo--P 1.08        1.12    satisfactory                             38     Fe--Ru--P 1.06        1.07    satisfactory                             39     Fe--Rh--P 1.04        1.04    satisfactory                             40     Fe--Pd--P 1.05        1.08    satisfactory                             41     Fe--Hf--P 1.08        1.09    satisfactory                             42     Fe--Ta--P 1.07        1.08    satisfactory                             43     Fe--W--P  1.09        1.10    satisfactory                             44     Fe--Re--P 1.04        1.09    satisfactory                             45     Fe--Os--P 1.06        1.06    satisfactory                             46     Fe--Ir--P 1.07        1.09    satisfactory                             ______________________________________                                    

As shown in Table 1, the dies of this embodiment possess long durabilitywhich was not possible using conventional materials. This is one of themajor characteristics of this invention.

A Ni-P binary alloy film was formed as the cutting layer on the basematerial of cemented carbide by the electroless plating method, and thePt-Ir alloy film was used as a protective coat to form the die. This diewas placed in the press-molding machine shown in FIG. 2. Thepress-molding process took place under the same conditions as above, andthe accuracy of the die was evaluated. The results of this comparativeexperiment are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        1      Ni--P     1.03        6.27    Enlarged                                        plated                        crack                                           film                                                                   ______________________________________                                    

As shown as comparative Sample No. 1 in Table 2, the conventionalmolding die comprises a cutting layer of electroless Ni-P plated filmcut into a transcriptional surface which is then coated with a Pt-Iralloy film for protection. The glass does not adhere to this die, butthe plated surface began to crack after being press-molded severaltimes. After press-molding only 100 times, the crack on the platedsurface enlarged more and more. The die did not stand any more usebecause the crack was transcribed on the lens, thereby deteriorating thequality of the lens.

This is due to the fact that Ni-P plated film which was used as thecutting layer did not have sufficient heat resistance so that Ni-Pplated film can not withstand the heat cycle of the press-moldingprocess when the glass having a high melting point is press-moldedrepeatedly.

On the other hand, according to the molding dies shown in inventionSample Nos. 2 to No. 46 of Table 1, the dies did not crack even afterbeing press-molded 10,000 times, and the surface condition remainedalmost the same. In addition, the surface roughness had hardly changed.It shows that these dies can press-mold glass having a high meltingpoint, such as SK-12.

The dies in this embodiment have enhanced the free-cutting property byincluding P in the film material of the cutting layer and improved theheat resistance by forming the cutting layer with materials of ternaryalloy films. In this way, all the requirements which are necessary topress-mold the above-mentioned glass optical elements directly with highaccuracy were met. It enabled press-molding a large quantity of glassoptical elements having high melting points and shapes which wasimpossible using conventional methods.

In this embodiment, cemented carbide mainly consisting of WC was used asthe base material of the press-molding die. It goes without saying thatany other material can be used to attain the same results as long as thematerial has heat resistance and sufficient strength to withstand thepress-molding process of optical glass. However, it is preferable to usecemented carbide mainly consisting of WC, cermet mainly consisting ofTiN or TiC, or WC sintered compact.

As far as the protective layer is concerned, Pt-Ir was used in thisembodiment, but the same results could be attained by using an alloyfilm of precious metal which includes at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta.

As a result, by press-molding glass by means of the press-molding die ofthis invention, it is possible to press-mold a large quantity of glassoptical elements having high melting points and shapes which aredifficult to attain by a grinding process.

EXAMPLE 2

The dimension and the structure of a die used in this embodiment areexactly the same as in the first embodiment except for the material usedfor the cutting layer and the protective layer. The same press-moldingmachine was used as in FIG.. 2.

The cutting layer used in this embodiment is a Ni-B ternary alloy, aCo-B ternary alloy, or a Fe-B ternary alloy.

In particular, it is possible to use Ni-B ternary alloys, for example,Ni-Si-B, Ni-Ti-B, Ni-Cu-B, Ni-Zr-B, Ni-Nb-B, Ni-Mo-B, Ni-Ru-B, Ni-Rh-B,Ni-Pd-B, Ni-Hf-B, Ni-Ta-B, Ni-W-B, Ni-Re-B, Ni-Os-B, and Ni-Ir-B.

It is also possible to use Co-B ternary alloys, for example, Co-Si-B,Co-Ti-B, Co-Cu-B, Co-Zr-B, Co-Nb-B, Co-Mo-B, Co-Ru-B, Co-Rh-B, Co-Pd-B,Co-Hf-B, Co-Ta-B, Co-W-B, Co-Re-B, Co-Os-B, and Co-Ir-B.

Furthermore, Fe-B ternary alloys can also be used, for example, Fe-Si-B,Fe-Ti-B, Fe-Cu-B, Fe-Zr-B, Fe-Nb-B, Fe-Mo-B, Fe-Ru-B, Fe-Rh-B, Fe-Pd-B,Fe-Hf-B, Fe-Ta-B, Fe-W-B, Fe-Re-B, Fe-Os-B, and Fe-Ir-B.

In practice, these alloys can be used to form cutting layers when theyare processed with a thickness of about 15 μm by the sputtering method.

Furthermore, a Pt-Os alloy protective layer is formed with a thicknessof 3 μm on the cutting layer by the sputtering method.

In order to form the cutting layer of ternary alloys on the basematerial of the molding die, the same procedure as in the firstembodiment is used.

First, a Ni-B or Co-B plated layer (percentage content of B=about 12 wt%) is formed with a thickness of about 0.5 mm by an electroless platingmethod on a Ni chip having a size of 10 mm×10 mm×1 mm. Thus, a Ni-B chipor a Co-B chip is formed. Then, 40 pieces of these chips are arrangedequally on top of disk targets of Si, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Bd,Hf, Ta, W, Re, Os or Ir having a diameter of 6 inches. They are used asthe target materials in the sputtering process.

In order to form a cutting layer of Fe-B ternary alloys, 40 pieces ofFeB compound chips having sizes of 10 mm×10 mm×1 mm are arranged equallyon top of disk targets consisting of the various materials mentionedabove to form different kinds of ternary alloy films. Similarly, thesealloy films were formed into transcription surfaces with high accuracyusing a diamond tool.

A cross-sectional view of the die for press-molding glass opticalelements produced by this method is shown in FIG. 3 where Ni-Ti-B alloyfilm is used as the cutting layer. Referring to FIG. 3, referencenumeral 31 denotes a Pt-Os alloy protective layer covering the presssurface; 32, a Ni-Ti-B alloy cutting layer; and 33, a base material ofcemented carbide.

These dies are placed in the press-molding machine shown in FIG. 2.Then, dense barium crown glass (SK-12) which was processed into aspherical shape having a radius of 1 mm was molded under the samemolding conditions as in the first example.

After repeating this press-molding process 10,000 times, upper and lowerdies 23, 25 were removed from the press-molding machine and thecondition of the pressed surfaces were observed with an opticalmicroscope. And then, the surface roughness (RMS value, nm) of thepressed surface was measured, and the accuracy of each die wasevaluated. The results are shown in Table 4 (a) and (b).

                  TABLE 4 (a)                                                     ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        48     Ni--Si--B 1.05        1.07    satisfactory                             49     Ni--Ti--B 1.04        1.05    satisfactory                             50     Ni--Cu--B 1.04        1.05    satisfactory                             51     Ni--Zr--B 1.04        1.05    satisfactory                             52     Ni--Nb--B 1.02        1.04    satisfactory                             53     Ni--Mo--B 1.06        1.07    satisfactory                             54     Ni--Ru--B 1.01        1.03    satisfactory                             55     Ni--Rh--B 1.05        1.06    satisfactory                             56     Ni--Pd--B 1.06        1.07    satisfactory                             57     Ni--Hf--B 1.03        1.04    satisfactory                             58     Ni--Ta--B 1.02        1.03    satisfactory                             59     Ni--W--B  1.02        1.03    satisfactory                             60     Ni--Re--B 1.04        1.05    satisfactory                             61     Ni--Os--B 1.06        1.07    satisfactory                             62     Ni--Ir--B 1.04        1.05    satisfactory                             63     Co--Si--B 1.01        1.02    satisfactory                             64     Co--Ti--B 1.03        1.04    satisfactory                             65     Co--Cu--B 1.02        1.03    satisfactory                             66     Co--Zr--B 1.05        1.08    satisfactory                             67     Co--Nb--B 1.01        1.13    satisfactory                             68     Co--Mo--B 1.04        1.05    satisfactory                             69     Co--Ru--B 1.02        1.03    satisfactory                             70     Co--Rh--B 1.02        1.03    satisfactory                             71     Co--Pd--B 1.02        1.04    satisfactory                             72     Co--Hf--B 1.04        1.06    satisfactory                             73     Co--Ta--B 1.05        1.06    satisfactory                             74     Co--W--B  1.04        1.05    satisfactory                             75     Co--Re--B 1.01        1.04    satisfactory                             76     Co--Os--B 1.08        1.11    satisfactory                             77     Co--Ir--B 1.06        1.08    satisfactory                             ______________________________________                                    

                  TABLE 4 (b)                                                     ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        78     Fe--Si--B 1.05        1.06    satisfactory                             79     Fe--Ti--B 1.04        1.05    satisfactory                             80     Fe--Cu--B 1.03        1.04    satisfactory                             81     Fe--Zr--B 1.04        1.05    satisfactory                             82     Fe--Nb--B 1.05        1.06    satisfactory                             83     Fe--Mo--B 1.03        1.03    satisfactory                             84     Fe--Ru--B 1.02        1.03    satisfactory                             85     Fe--Rh--B 1.04        1.06    satisfactory                             86     Fe--Pd--B 1.06        1.08    satisfactory                             87     Fe--Hf--B 1.07        1.08    satisfactory                             88     Fe--Ta--B 1.02        1.04    satisfactory                             89     Fe--W--B  1.05        1.06    satisfactory                             90     Fe--Re--B 1.04        1.06    satisfactory                             91     Fe--Os--B 1.06        1.06    satisfactory                             92     Fe--Ir--B 1.07        1.09    satisfactory                             ______________________________________                                    

Furthermore, a comparative experiment was conducted. A Ni-Binary alloyfilm was formed as the cutting layer on the base material of cementedcarbide by the electroless plating method, and the Pt-Os alloy film asin this embodiment was used as a protective layer to form the die. Thesame press-molding process took place as in this embodiment, and theaccuracy of the die was evaluated. The results of this comparativeexperiment are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        47     Ni--B     1.03        6.84    Enlarged                                        plated                        crack                                           film                                                                   ______________________________________                                    

As shown in comparative Sample No. 47, the die comprises binary alloyplated film of eletroless Ni-B as the cutting layer which is then coatedwith a Pt-Os alloy film. The glass does not adhere to this die, but theplated film began to crack after being press-molded several times. Afterpress-molding 100 times, the crack on the plated surface enlarged. Thedie did not stand any more use because the crack was transcribed on thelens, thereby deteriorating the quality of the lens.

This is due to the fact that Ni-B binary alloy film which was used asthe cutting layer did not have sufficient heat resistance to withstandthe heat cycle of the press-molding process when the glass having a highmelting point is press-molded repeatedly.

On the other hand, according to the dies of this invention shown ininvention Sample Nos. 48 to No. 92, the dies did not crack even afterpress-molded 10,000 times and the surface condition remained almost thesame.

In addition, the surface roughness had hardly changed. It shows thatthese dies can press-mold glass having a high melting point, such asSK-12.

As a result, by press-molding glass by means of the press-molding glassof this invention, it is possible to press-mold a large quantity ofglass optical elements having high melting points and shapes which aredifficult to attain by a grinding process.

As described above, the dies in this embodiment have enhanced thefree-cutting property by including B in the cutting alloy layer andimproved the heat resistance by forming ternary alloy films. In thisway, all the requirements which are necessary to press-mold directly theabove-mentioned glass optical elements with high accuracy were met. Itenabled press-molding a large quantity of glass optical elements havinghigh melting points and shapes which was impossible to be molded byconventional methods.

Cemented carbide mainly consisting of WC was used as the base materialof the die for press-molding in this embodiment. It goes without sayingthat any other material can be used to attain the same results providedthat it has heat resistance and sufficient strength to withstand thepress-molding process for optical glass. However, it is preferable touse cemented carbide consisting mainly of WC, cermet mainly consistingof TiN or TiC, or WC sintered compact.

As far as the protective layer is concerned, Pt-Os was used in thisembodiment, but the same results could be attained by using an alloyfilm of precious metal which includes at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta.

EXAMPLE 3

The die for press-molding of this embodiment is exactly the same as inthe first embodiment except for the composition of material used for thealloy cutting layer and the protective layer.

The cutting layer used in this embodiment is a Cu binary alloy layer asthe cutting layer. In particular, suitable Cu binary alloys include, forexample, Cu-Ni, Cu-Co, Cu-Fe, Cu-Si, Cu-Ti, Cu-Zr, Cu-Nb, Cu-Mo, Cu-Ru,Cu-Rh, Cu-Pd, Cu-Hf, Cu-Ta, Cu-W, Cu-Re, and Cu-Os.

In order to form these binary alloy films, a Cu chip having a size of 10mm×10 mm×1 mm is arranged equally on top of disk targets of Ni, Co, Fe,Si, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re or Os having a diameter of6 inches. This is used as the target material for the sputteringprocess.

At the same time, by changing the number of the Cu-chip arranged on thedisk targets, it is possible to control the composition of Cu binaryalloys being formed.

A Pt-Rh alloy protective layer was formed with a thickness of 3 μm onthe cutting layer by the sputtering method. The thickness of the cuttinglayer consisting of the Cu binary alloy was determined to be about 15μm.

A cross-sectional view of the die for press-molding in this embodimentis shown in FIG. 4. Referring to FIG. 4, reference numeral 41 denotes aPt-Rh alloy protective layer covering the press surface; 42, a CU-Tialloy cutting film; 43, a base material of cemented carbide.

These dies are placed in the press-molding machine shown in FIG. 2.Then, dense barium crown glass (SK-12) 24 which was processed into aspherical shape with a radius of 1 mm was press-molded under the sameconditions as in the first embodiment.

After repeating this press-molding process 10,000 times, upper and lowerdies 23, 25 were removed from the press-molding machine, and thecondition of the pressed surfaces was observed with an opticalmicroscope. At this moment, surface roughness (RMS value, nm) of thepressed surface was measured, and the accuracy of each die wasevaluated.

The results are shown in Table 6 (a) and (b). The percentage content ofCu in the composition was controlled within the range of 20 to 80 at %.This is due to the fact that a diamond tool is worn when cut with a Cucontent of less than 20 at %, while the shape is deformed when pressedwith Cu content of more than 80 at % due to hardness deterioration.

As mentioned above, the percentage content of Cu was controlled bychanging the number of the Cu-chip arranged on disk targets.

                  TABLE 6 (a)                                                     ______________________________________                                        Results of Press Experiment                                                               Surface  After pressing 10,000 times                                                roughness  Surface                                          Sample                                                                              Type        before pressing                                                                          roughness                                                                             Surface                                  No.   of die      (RMS, nm)  (RMS, nm)                                                                             condition                                ______________________________________                                        94    Cu(20)--Ni(80)                                                                            1.03       1.04    satisfactory                             95    Cu(50)--Ni(50)                                                                            1.05       1.07    satisfactory                             96    Cu(80)--Ni(20)                                                                            1.04       1.05    satisfactory                             97    Cu(20)--Co(80)                                                                            1.07       1.08    satisfactory                             98    Cu(50)--Co(50)                                                                            1.03       1.04    satisfactory                             99    Cu(80)--Co(20)                                                                            1.04       1.05    satisfactory                             100   Cu(20)--Fe(80)                                                                            1.06       1.07    satisfactory                             101   Cu(50)--Fe(50)                                                                            1.03       1.05    satisfactory                             102   Cu(80)--Fe(20)                                                                            1.02       1.03    satisfactory                             103   Cu(20)--Si(80)                                                                            1.05       1.06    satisfactory                             104   Cu(50)--Si(50)                                                                            1.04       1.05    satisfactory                             105   Cu(80)--Si(20)                                                                            1.06       1.08    satisfactory                             106   Cu(20)--Ti(80)                                                                            1.05       1.07    satisfactory                             107   Cu(50)--Ti(50)                                                                            1.04       1.05    satisfactory                             108   Cu(80)--Ti(20)                                                                            1.06       1.07    satisfactory                             109   Cu(20)--Zr(80)                                                                            1.03       1.04    satisfactory                             110   Cu(50)--Zr(50)                                                                            1.05       1.07    satisfactory                             111   Cu(80)--Zr(20)                                                                            1.01       1.04    satisfactory                             112   Cu(20)--Nb(80)                                                                            1.07       1.08    satisfactory                             113   Cu(50)--Nb(50)                                                                            1.04       1.05    satisfactory                             114   Cu(80)--Nb(20)                                                                            1.01       1.03    satisfactory                             115   Cu(20)--Mo(80)                                                                            1.05       1.06    satisfactory                             ______________________________________                                    

                  TABLE 6 (a)                                                     ______________________________________                                        Results of Press Experiment                                                               Surface  After pressing 10,000 times                                                roughness  Surface                                          Sample                                                                              Type        before pressing                                                                          roughness                                                                             Surface                                  No.   of die      (RMS, nm)  (RMS, nm)                                                                             condition                                ______________________________________                                        116   Cu(50)--Mo(50)                                                                            1.04       1.04    satisfactory                             117   Cu(80)--Mo(20)                                                                            1.05       1.07    satisfactory                             118   Cu(20)--Ru(80)                                                                            1.05       1.06    satisfactory                             119   Cu(50)--Ru(50)                                                                            1.05       1.06    satisfactory                             120   Cu(80)--Ru(20)                                                                            1.07       1.08    satisfactory                             121   Cu(20)--Rh(80)                                                                            1.03       1.04    satisfactory                             122   Cu(50)--Rh(50)                                                                            1.08       1.09    satisfactory                             123   Cu(80)--Rh(20)                                                                            1.05       1.07    satisfactory                             124   Cu(20)--Pd(80)                                                                            1.03       1.05    satisfactory                             125   Cu(50)--Pd(50)                                                                            1.06       1.07    satisfactory                             126   Cu(80)--Pd(20)                                                                            1.01       1.03    satisfactory                             127   Cu(20)--Hf(80)                                                                            1.06       1.08    satisfactory                             128   Cu(50)--Hf(50)                                                                            1.06       1.06    satisfactory                             129   Cu(80)--Hf(20)                                                                            1.07       1.09    satisfactory                             130   Cu(20)--Ta(80)                                                                            1.02       1.05    satisfactory                             131   Cu(50)--Ta(50)                                                                            1.03       1.06    satisfactory                             132   Cu(80)--Ta(20)                                                                            1.04       1.05    satisfactory                             133   Cu(20)--W(80)                                                                             1.02       1.04    satisfactory                             134   Cu(50)--W(50)                                                                             1.06       1.07    satisfactory                             135   Cu(80)--W(20)                                                                             1.05       1.08    satisfactory                             136   Cu(20)--Re(80)                                                                            1.01       1.03    satisfactory                             137   Cu(50)--Re(50)                                                                            1.04       1.06    satisfactory                             138   Cu(80)--Re(20)                                                                            1.05       1.05    satisfactory                             139   Cu(20)--Os(80)                                                                            1.07       1.08    satisfactory                             140   Cu(50)--Os(50)                                                                            1.01       1.03    satisfactory                             141   Cu(80)--Os(20)                                                                            1.05       1.07    satisfactory                             ______________________________________                                    

Furthermore, a comparative experiment was conducted. As in the firstembodiment, a Ni-P film was formed as the cutting layer on the basematerial of cemented carbide by the electroless plating method, and thePt-Rh alloy film was used as a protective layer to form the die. Thepress-molding process took place repeatedly under exactly the samemolding conditions. The results of this experiment are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        93     Ni--P     1.03        7.19    Enlarged                                        plated                        crack                                           film                                                                   ______________________________________                                    

When the die used in comparative sample No. 93 was molded, the glass didnot adhere to the die, but the plated layer began to crack after beingpress-molded several times. After press-molding 100 times, the crack onthe plated surface enlarged. The die did not stand any more use becausethe crack was transcribed on the lens, thereby deteriorating the qualityof the lens.

This is due to the fact that Ni-P plated film which was used as thecutting layer did not have sufficient heat resistance to withstand theheat cycle of the press-molding process when the glass having a highmelting point is press-molded repeatedly.

On the other hand, according to the dies of this invention shown inSample Nos. 94 to No. 141, the dies did not crack even after beingpress-molded 10,000 times, and the surface condition remained almost thesame. The surface roughness has hardly changed. It shows that these diescan press-mold glass having a high melting point, such as SK-12.

As a result, by press-molding glass by means of the press-molding glassof this invention, it is possible to press-mold a large quantity ofglass optical elements having high melting points and shapes which aredifficult to attain by a grinding process.

Accordingly, all the requirements which are necessary to directlypress-mold the above-mentioned glass optical elements with high accuracywere met. It enabled press-molding a large quantity of glass opticalelements having high melting points and shapes which was impossibleusing conventional methods.

Cemented carbide consisting mainly of WC was used as the base materialof the die for press-molding in this embodiment. It goes without sayingthat any other material can be used to attain the same results as longas it has heat resistance and sufficient strength to withstand thepress-molding process of optical glass. However, it is preferable to usecemented carbide consisting mainly of WC, cermet consisting mainly ofTiN or TiC, or WC sintered compact.

As far as the protective layer is concerned, Pt-Rh was used in thisembodiment, but the same results could be attained by using an alloyfilm of precious metal which includes at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta.

EXAMPLE 4

The die for press-molding in this embodiment is exactly the same as inthe first embodiment except for the composition of material used for thealloy cutting layer and the protective layer.

The cutting layer used in this embodiment is a Si binary alloy layer. Inparticular, it is possible to use Si binary alloys for the cuttinglayer, for example, Si-Ni, Si-Co, Si-Fe, Si-Cu, Si-Ti, Si-Zr, Si-Nb,Si-Mo, Si-Ru, Si-Rh, Si-Pd, Si-Hf, Si-Ta, Si-W, Si-Re, and Si-Os.

In order to form these binary alloy films, a Si chip having a size of 10mm×10 mm×1 mm is arranged equally on disk targets of Ni, Co, Fe, Si, Ti,Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re or Os having a diameter of 6inches. This is used as the target material in the sputtering process.

By changing the number of the Si chip arranged on the disk targets, itis possible to control the composition of Si binary alloys being formed.

A Pt-Rh alloy protective layer was formed with a thickness of 3 μm onthe cutting layer by the sputtering method. The thickness of the cuttinglayer consisting of Si binary alloys was determined to be about 15 μm.

A cross-sectional view of the die for press-molding in this embodimentis shown in FIG. 5. Referring to FIG. 5, reference numeral 51 denotes aPt-Pd alloy protective layer covering the press surface; 52, a Si-Taalloy cutting film; 53, a base material of cemented carbide.

These dies are placed in the press-molding machine shown in FIG. 2.Then, dense barium crown glass (SK-12) 24 which was processed into aspherical shape with a radius of 1 mm was press-molded under the sameconditions as in the first embodiment.

After repeating this press-molding process 10,000 times, upper and lowerdies 23, 25 were removed from the press-molding machine and thecondition of the pressed surfaces was observed with an opticalmicroscope. At the same time, the surface roughness (RMS value, nm) ofthe pressed surface was measured, and the accuracy of each die wasevaluated.

The results are shown in Table 8 (a) to (b). The percentage content ofSi in the composition was controlled within the range of 20 to 80 at %.This is due to the fact that a diamond tool is worn when cut with a Sicontent of less than 20 at %, while the shape is deformed when pressedwith a Si content of more than 80 at % due to hardness deterioration.

As described above, the percentage content of Si in the cutting layerwas changed by controlling the number of the Si chips arranged on thedisk targets.

                  TABLE 8 (a)                                                     ______________________________________                                        Results of Press Experiment                                                               Surface  After pressing 10,000 times                                                roughness  Surface                                          Sample                                                                              Type        before pressing                                                                          roughness                                                                             Surface                                  No.   of die      (RMS, nm)  (RMS, nm)                                                                             condition                                ______________________________________                                        143   Si(20)--Ni(80)                                                                            1.03       1.04    satisfactory                             144   Si(50)--Ni(50)                                                                            1.05       1.07    satisfactory                             145   Si(80)--Ni(20)                                                                            1.04       1.05    satisfactory                             146   Si(20)--Co(80)                                                                            1.07       1.08    satisfactory                             147   Si(50)--Co(50)                                                                            1.03       1.04    satisfactory                             148   Si(80)--Co(20)                                                                            1.04       1.05    satisfactory                             149   Si(20)--Fe(80)                                                                            1.06       1.07    satisfactory                             150   Si(50)--Fe(50)                                                                            1.03       1.05    satisfactory                             151   Si(80)--Fe(20)                                                                            1.02       1.03    satisfactory                             152   Si(20)--Cu(80)                                                                            1.05       1.06    satisfactory                             153   Si(50)--Cu(50)                                                                            1.03       1.05    satisfactory                             154   Si(80)--Cu(20)                                                                            1.05       1.07    satisfactory                             155   Si(20)--Ti(80)                                                                            1.08       1.09    satisfactory                             156   Si(50)--Ti(50)                                                                            1.06       1.08    satisfactory                             157   Si(80)--Ti(20)                                                                            1.03       1.06    satisfactory                             158   Si(20)--Zr(80)                                                                            1.03       1.04    satisfactory                             159   Si(50)--Zr(50)                                                                            1.04       1.07    satisfactory                             160   Si(80)--Zr(20)                                                                            1.02       1.06    satisfactory                             161   Si(20)--Nb(80)                                                                            1.07       1.08    satisfactory                             162   Si(50)--Nb(50)                                                                            1.06       1.08    satisfactory                             163   Si(80)--Nb(20)                                                                            1.04       1.07    satisfactory                             ______________________________________                                    

                  TABLE 8 (b)                                                     ______________________________________                                        Results of Press Experiment                                                               Surface  After pressing 10,000 times                                                roughness  Surface                                          Sample                                                                              Type        before pressing                                                                          roughness                                                                             Surface                                  No.   of die      (RMS, nm)  (RMS, nm)                                                                             condition                                ______________________________________                                        164   Si(20)--Mo(80)                                                                            1.02       1.05    satisfactory                             165   Si(50)--Mo(50)                                                                            1.07       1.08    satisfactory                             166   Si(80)--Mo(20)                                                                            1.05       1.08    satisfactory                             167   Si(20)--Ru(80)                                                                            1.04       1.05    satisfactory                             168   Si(50)--Ru(50)                                                                            1.01       1.03    satisfactory                             169   Si(80)--Ru(20)                                                                            1.04       1.06    satisfactory                             170   Si(20)--Rh(80)                                                                            1.05       1.07    satisfactory                             171   Si(50)--Rh(50)                                                                            1.04       1.06    satisfactory                             172   Si(80)--Rh(20)                                                                            1.03       1.05    satisfactory                             173   Si(20)--Pd(80)                                                                            1.04       1.07    satisfactory                             174   Si(50)--Pd(50)                                                                            1.03       1.05    satisfactory                             175   Si(80)--Pd(20)                                                                            1.03       1.06    satisfactory                             176   Si(20)--Hf(80)                                                                            1.04       1.05    satisfactory                             178   Si(50)--Hf(50)                                                                            1.06       1.07    satisfactory                             179   Si(80)--Hf(20)                                                                            1.05       1.08    satisfactory                             180   Si(20)--Ta(80)                                                                            1.04       1.07    satisfactory                             181   Si(50)--Ta(50)                                                                            1.04       1.06    satisfactory                             182   Si(80)--Ta(20)                                                                            1.04       1.05    satisfactory                             183   Si(20)--W(80)                                                                             1.02       1.04    satisfactory                             184   Si(50)--W(50)                                                                             1.06       1.07    satisfactory                             185   Si(80)--W(20)                                                                             1.05       1.08    satisfactory                             186   Si(20)--Re(80)                                                                            1.01       1.03    satisfactory                             187   Si(50)--Re(50)                                                                            1.04       1.06    satisfactory                             188   Si(80)--Re(20)                                                                            1.05       1.05    satisfactory                             ______________________________________                                    

Furthermore, a comparative experiment was conducted. As in the firstembodiment, a Ni-P plated film was formed as the cutting layer on thebase material of cemented carbide by the electroless plating method, andthe Pt-Pd alloy film was used as a protective layer to form the die. Thepress-molding process took place repeatedly under exactly the samepress-molding conditions. The results of this experiment are shown inTable 7.

                  TABLE 7                                                         ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        142    Ni--P     1.03        5.96    Enlarged                                        plated                        crack                                           film                                                                   ______________________________________                                    

When the die used in comparative Sample No. 142 was molded, the glassdid not adhere to this die, but the plated layer began to crach afterpress-molded several times. After press-molding 100 times, the crack onthe plated surface enlarged. The die did not stand any more use becausethe crack was transcribed on the lens, thereby deteriorating the qualityof the lens.

This is due to the fact that Ni-P plated film which was used as thecutting layer has not sufficient heat resistance to withstand the heatcycle of the press-molding process when the glass having a high meltingpoint is press-molded repeatedly.

On the other hand, according to the dies of this invention shown inSample Nos. 143 to No. 191, the dies did not crack even afterpress-molded 10,000 times and the surface condition remained almost thesame. The surface roughness has hardly changed. It shows that these diescan press-mold glass having a high melting point, such as SK-12.

As a result, by press-molding glass by means of the press-molding glassof this invention, it is possible to press-mold a large quantity ofglass optical elements having high melting points and shapes which aredifficult to attain by a grinding process.

Accordingly, all the requirements which are necessary to directlypress-mold the above-mentioned glass optical elements with high accuracywere met. It enabled to press-mold a large quantity of glass opticalelements having high melting points and shapes which were impossible tobe molded in the past.

Cemented carbide consisting mainly of WC was used as the base materialof the die for press-molding in this embodiment. It goes without sayingthat any other material can be used to attain the same results that hasheat resistance and sufficient strength to withstand the press-moldingprocess of optical glass. However, it is preferable to use cementedcarbide consisting mainly of WC, cermet mainly consisting of TiN or TiC,or WC sintered compact.

EXAMPLE 5

The dimension and the structure of the die used in this embodiment areexactly the same as in the first embodiment except for the material usedfor the cutting layer and the protective layer. The same press-moldingmachine was used as in FIG. 2.

In this embodiment, an amorphous binary alloy layer is used as thecutting layer consisting of Ni, Co, Cr. Ta, Mo, Ti, W, Nb, V or Cu.

As for an amorphous binary alloy layer with Ni, suitable Ni alloysinclude, for example, Ni-Co, Ni-Cr, Ni-Ta, Ni-Mo, Ni-Ti, Ni-W, Ni-Nb,Ni-V, Ni-Cu, and Ni-Al.

As for an amorphous binary alloy layer with Co, suitable Co alloysinclude, for example, Co-Cr, Co-Ta, Co-Mo, Co-Ti, Co-W, Co-Nb, Co-V,Co-Cu, and Co-Al.

As for an amorphous binary alloy layer with Cr, suitable Cr alloysinclude, for example, Cr-Ta, Cr-Mo, Cr-Ti, Cr-M, Cr-Nb, Cr-V, Cr-Cu, andCr-Al.

As for an amorphous binary alloy layer with Ta, suitable Ta alloysinclude, for example, Ta-Mo, Ta-Ti, Ta-W, Ta-Nb, Ta-V, Ta-Cu, and Ta-Al.

As for an amorphous binary alloy layer with Mo, suitable Mo alloysinclude, for example, Mo-Ti, Mo-W, Mo-Nb, Mo-V, Mo-Cu, and Mo-Al.

As for an amorphous binary alloy layer with Ti, suitable Ti alloysinclude, for example, Ti-W, Ti-Nb, Ti-V, Ti-Cu, and Ti-Al.

As for an amorphous binary alloy layer with W, suitable W alloysinclude, for example, W-Nb, W-V, W-Cu, and W-Al.

As for an amorphous binary alloy layer with Nb, suitable Nb alloysinclude, for example, Nb-V, Nb-Cu, and Nb-Al.

As for an amorphous binary alloy layer with V, suitable V alloysinclude, for example, V-Cu and V-Al.

As for an amorphous binary alloy layer with Cu, suitable Cu alloysinclude, for example, Cu-Al alloy film.

The reason for putting the cutting layer in an amorphous condition isthat a grain boundary will not be present in the cutting layer in thiscondition. As a result, the cutting property of the cutting layerimproves considerably, and the cutting tools will not be worn so much,thereby conducting the cutting process with high accuracy.

In this embodiment, the above-mentioned amorphous alloy film was cutwith use of a diamond tool forming into an extremely accurate surface.

By cutting the amorphous alloy film in this way, a hollow-shaped die of1 mm radius of curvature was obtained with high accuracy which wasdifficult to attain with a conventional grinding process. In addition,this method required only 1/10 of the time needed for the conventionalgrinding process.

In practice, these amorphous alloys can be used to form cutting layersof molding dies when they are processed with a thickness of about 15 μmby the sputtering method.

Furthermore, a Pt-Ru alloy protective layer was formed with a thicknessof 3 μm on the cutting layer by the sputtering method in thisembodiment.

A cross-sectional view of a die for press-molding produced in this wayis shown in FIG. 6 in which a Cr-Cu alloy film is used for the cuttinglayer. Referring to FIG. 6, reference numeral 61 denotes a Pt-Ru alloyprotective layer covering the press surface; 62, a Cr-Cu alloy cuttingfilm; 63, a base material of cemented carbide.

These dies are placed in the press-molding machine shown in FIG. 2.Then, dense barium crown glass (SK-12) 24 which was processed into aspherical shape with a radius of 1 mm was molded under the sameconditions as in all the above-mentioned embodiments.

After repeating this press-molding process 10,000 times, upper and lowerdies 23, 25 were removed from the press-molding machine, and thecondition of the pressed surfaces was observed with an opticalmicroscope. At this moment, the surface roughness (RMS value, nm) of thepressed surface was measured, and the accuracy of each die wasevaluated. The results are shown in Table 10 (a), (b) and (c).

                  TABLE 10 (a)                                                    ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        193    Ni--Co    1.06        1.07    satisfactory                             194    Ni--Cr    1.04        1.08    satisfactory                             195    Ni--Ta    1.09        1.13    satisfactory                             196    Ni--Mo    1.07        1.09    satisfactory                             197    Ni--Ti    1.03        1.05    satisfactory                             198    Ni--W     1.04        1.08    satisfactory                             199    Ni--Nb    1.08        1.09    satisfactory                             200    Ni--V     1.08        1.12    satisfactory                             201    Ni--Cu    1.03        1.07    satisfactory                             202    Ni--Al    1.04        1.06    satisfactory                             203    Co--Cr    1.08        1.10    satisfactory                             204    Co--Ta    1.05        1.09    satisfactory                             205    Co--Mo    1.04        1.06    satisfactory                             206    Co--Ti    1.03        1.06    satisfactory                             207    Co--W     1.02        1.07    satisfactory                             208    Co--Nb    1.01        1.05    satisfactory                             209    Co--V     1.06        1.08    satisfactory                             210    Co--Cu    1.06        1.09    satisfactory                             211    Co--Al    1.04        1.06    satisfactory                             212    Cr--Ta    1.03        1.06    satisfactory                             213    Cr--Mo    1.04        1.08    satisfactory                             ______________________________________                                    

                  TABLE 10 (b)                                                    ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        214    Cr--Ti    1.02        1.06    satisfactory                             215    Cr--W     1.04        1.05    satisfactory                             216    Cr--Nb    1.03        1.07    satisfactory                             217    Cr--V     1.06        1.08    satisfactory                             218    Cr--Cu    1.06        1.06    satisfactory                             219    Cr--Al    1.04        1.05    satisfactory                             220    Ta--Mo    1.06        1.08    satisfactory                             221    Ta--Ti    1.05        1.08    satisfactory                             222    Ta--W     1.05        1.06    satisfactory                             223    Ta--Nb    1.04        1.09    satisfactory                             224    Ta--V     1.05        1.07    satisfactory                             225    Ta--Cu    1.02        1.06    satisfactory                             226    Ta--Al    1.05        1.08    satisfactory                             227    Mo--Ti    1.04        1.07    satisfactory                             228    Mo--W     1.03        1.04    satisfactory                             229    Mo--Nb    1.04        1.09    satisfactory                             230    Mo--V     1.09        1.15    satisfactory                             231    Mo--Cu    1.06        1.08    satisfactory                             232    Mo--Al    1.05        1.08    satisfactory                             233    Ti--W     1.01        1.06    satisfactory                             234    Ti--Nb    1.07        1.08    satisfactory                             235    Ti--V     1.07        1.09    satisfactory                             236    Ti--Cu    1.01        1.05    satisfactory                             237    Ti--Al    1.06        1.10    satisfactory                             238    W--Nb     1.07        1.09    satisfactory                             239    W--V      1.07        1.08    satisfactory                             240    W--Cu     1.04        1.09    satisfactory                             241    W--Al     1.04        1.07    satisfactory                             242    Nb--V     1.02        1.06    satisfactory                             243    Nb--Cu    1.06        1.08    satisfactory                             ______________________________________                                    

                  TABLE 10 (c)                                                    ______________________________________                                        Results of Press Experiment                                                                      After pressing 10,000 times                                                 Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        244    Nb--Al    1.04        1.07    satisfactory                             245    V--Cu     1.04        1.06    satisfactory                             246    V--Al     1.05        1.08    satisfactory                             247    Cu--Al    1.08        1.12    satisfactory                             ______________________________________                                    

Furthermore, a comparative experiment was conducted in crystalline filmsconsisting of Ni-Co, Ni-Cr, Ni-Ta, Ni-Mo, Ni-W, Ni-Nb, Ni-V, Ni-Cu,Ni-Al, Co-Cr, Co-Ta, Co-Mo, Co-W, Co-Nb, Co-V, Co-Cu, Co-Al, Cr-Ta,Cr-Mo, Cr-Tl, Cr-W, Cr-V, Cr-Cu, Cr-Al, Ta-Mo, Ta-Ti, Ta-W, Ta-Nb, Ta-V,Ta-Al, Mo-Ti, Mo-W, Mo-Nb, Mo-V, Mo-Cu, Mo-Al, Ti-W, Ti-Nb, Ti-Cu,Ti-Al, W-Nb, W-V, W-Cu, W-Al, Nb-V, Nb-Cu, Nb-Al, V-Cu, V-Al, and Cu-Alwere formed on the base material of cemented carbide to conduct thecutting process. However, due to the strong cutting force and attritionof tools, it was not possible to form the desired shape.

Therefore, a Ni-P plated film was formed as the cutting layer on thebase material of cemented carbide by the electroless plating method andPt-Ru alloy film was used as the protective layer for the die as in thefirst embodiment. The same press-molding process was performedrepeatedly, and the accuracy of each die was evaluated. The results areshown in Table 9.

                  TABLE 9                                                         ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        192    Ni--P     1.04        8.41    Enlarged                                        plated                        crack                                           film                                                                   ______________________________________                                    

When the die used in comparative Sample No. 192 was press-molded, theglass did not adhere to this die, but the plated layer began to crackafter being press-molded several times. After press-molding 100 times,the crack on the plated surface enlarged. The die did not stand any moreuse because the crack was transcribed on the lens, thereby deterioratingthe quality of the lens.

This is due to the fact that Ni-P plated film which was used as thecutting layer did not have sufficient heat resistance to withstand theheat cycle of the press-molding process when the glass having a highmelting point is press-molded repeatedly.

On the other hand, according to the dies of this invention shown inSample Nos. 193 to No. 247, the dies did not crack even afterpress-molded 10,000 times and the surface condition remained almost thesame. The surface roughness has hardly changed. It shows that these diescan press-mold glass having a high melting point, such as SK-12.

As a result, by press-molding glass by means of the press-molding glassof this invention, it is possible to press-mold a large quantity ofglass optical elements having high melting points and shapes which aredifficult to attain by a grinding process.

Accordingly, all the requirements which are necessary to press-mold theabove-mentioned glass optical elements directly with high accuracy weremet. It enabled press-molding a large quantity of glass optical elementshaving high melting points and shapes which was impossible usingconventional methods.

Cemented carbide consisting mainly of WC was used as the base materialof the die for press-molding in this embodiment. It goes without sayingthat any other material can be used to attain the same results providedthat it has heat resistance and sufficient strength to withstand thepress-molding process of optical glass. However, it is preferable to usecemented carbide consisting mainly of WC, cermet consisting mainly ofTiN or TiC, or WC sintered compact.

As far as the protective layer is concerned, Pt-Pd was used in thisembodiment, but the same results could be attained by using an alloyfilm of precious metal which includes at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta.

EXAMPLE 6

A die for press-molding in this embodiment has an intermediate layer onthe surface on which an alloy cutting layer and a protective layer areformed.

The dimensions of the die are the same as in the first embodiment.

In this embodiment, it is possible to use, for example, films of Ni,SiC, Tin, and Ta₂ O₅. In practice, an intermediate layer can be usedwhen it is formed with a thickness of about 1 μm by the sputteringmethod and so forth.

As for the cutting layer, it is possible to use, for example, alloyfilms of Ni-W-P, Ni-Cu-B, Cu-Ti, Si-Zr and amorphous alloy films ofNi-Mo.

These cutting layers are applicable when they are formed with athickness of 15 μm by the sputtering method.

The alloy cutting layer can be cut into a surface with extreme accuracywith use of a diamond tool. By cutting the alloy film in this way, ahollow-shaped die of 1 mm radius of curvature could be obtained withextreme accuracy which was difficult to attain in a conventionalgrinding process. In addition, this method required only 1/10 of thetime needed for the conventional grinding process.

A Pt-Ta alloy protective layer was formed with a thickness of 3 μm onthe cutting layer by the sputtering method.

A cross-sectional view of a die for press-molding produced in this wayis shown in FIG. 7 in which a SiC film is used for the intermediatelayer and a Cu-Ti alloy film for the cutting layer. Referring to FIG. 7,reference numeral 71 denotes a Pt-Ta alloy protective layer covering thepress surface; 72, a Cu-Ti alloy cutting film; 73, a SiC film; and 74, abase material of cemented carbide.

This die was used to press-mold dense barium crown glass (SK-12) 24which was processed into a spherical shape having a radius of 1 mm underthe same conditions as in the first embodiment.

After repeating this press-molding process 10,000 times, 30,000 times,and 50,000 times, upper and lower dies 23, 25 were removed from thepress-molding machine, and the condition of the pressed surfaces wasobserved with an optical microscope. At the same time, the surfaceroughness (RMS value, nm) of the pressed surface was measured, and theaccuracy of each die was evaluated. The results are shown in Table 12.

                                      TABLE 12                                    __________________________________________________________________________    Results of Press Experiment                                                                  Surface                                                                             Surface condition                                                       roughness                                                                           after pressing                                                      inter-                                                                            before                                                                              10,000                                                                              30,000                                                                              50,000                                       Sample                                                                             Type  mediate                                                                           pressing                                                                            times times times                                        No.  of die                                                                              layer                                                                             (RMS, nm)                                                                           (RMS, nm)                                                                           (RMS, nm)                                                                           (RMS, nm)                                    __________________________________________________________________________    254  Ni--W--P                                                                            Ni  1.05  1.07  1.08  1.09                                         255  Ni--W--P                                                                            SiC 1.06  1.06  1.08  1.08                                         256  Ni--W--P                                                                            TiN 1.03  1.04  1.04  1.05                                         257  Ni--W--P                                                                            Ta2O5                                                                             1.06  1.07  1.09  1.01                                         258  Ni--Cu--B                                                                           Ni  1.04  1.06  1.08  1.09                                         259  Ni--Cu--B                                                                           SiC 1.04  1.05  1.06  1.07                                         260  Ni--Cu--B                                                                           TiN 1.02  1.03  1.05  1.08                                         261  Ni--Cu--B                                                                           Ta2O5                                                                             1.04  1.04  1.07  1.08                                         262  Cu--Ti                                                                              Ni  1.04  1.05  1.07  1.09                                         263  Cu--Ti                                                                              SiC 1.04  1.06  1.07  1.08                                         264  Cu--Ti                                                                              TiN 1.03  1.03  1.06  1.07                                         265  Cu--Ti                                                                              Ta2O5                                                                             1.03  1.04  1.06  1.06                                         266  Si--Zr                                                                              Ni  1.04  1.05  1.07  1.10                                         267  Si--Zr                                                                              SiC 1.06  1.07  1.08  1.09                                         268  Si--Zr                                                                              TiN 1.05  1.05  1.06  1.08                                         269  Si--Zr                                                                              Ta2O5                                                                             1.05  1.06  1.08  1.09                                         270  Ni--Mo                                                                              Ni  1.04  1.05  1.07  1.08                                         271  Ni--Mo                                                                              SiC 1.04  1.05  1.07  1.09                                         272  Ni--Mo                                                                              TiN 1.03  1.03  1.05  1.07                                         273  Ni--Mo                                                                              Ta2O5                                                                             1.04  1.05  1.06  1.07                                         __________________________________________________________________________

As a comparative experiment, a Ni-P plated film was formed as thecutting layer on a base material of cemented carbide by the electrolessplating method, and Pt-Ta alloy film was used as a protective layer toform the die. The same press-molding process took place, and theaccuracy of each die was evaluated. The results are shown in Table 11.

                  TABLE 11                                                        ______________________________________                                        Results of Comparative Experiment                                                                After pressing 100 times                                                    Surface roughness                                                                         Surface                                          Sample Type      before pressing                                                                           roughness                                                                             Surface                                  No.    of die    (RMS, nm)   (RMS, nm)                                                                             condition                                ______________________________________                                        248    Ni--P     1.07        5.49    Transcribed                                     plated                        crack                                           film                                                                   ______________________________________                                    

When the molding die of comparative Sample No. 248 was molded, the glassdid not adhere to this die, but the plated layer began to crach afterpress-molded several times. After press-molding 100 times, the crack onthe plated surface enlarged. The die did not stand any more use becausethe crack was transcribed on the lens, thereby deteriorating the qualityof the lens.

Furthermore, the die in this embodiment has characteristics superior tothe dies shown in the embodiments 1 to 5, as shown in the following.

As the cutting layers in the embodiments 1 to 5 (i.e., Example 1 to 5),alloy films of Ni-W-P, Ni-Cu-B, Cu-Ti, Si-Zr, and Ni-Mo amorphous alloyfilms were formed using Pt-Ta alloy film as a protective layer. Afterpress-molding these dies 10,000 times, 30,000 times and 40,000 times,the condition of the pressed surfaces was observed with an opticalmicroscope. At the same time, the surface roughness (RMS value, nm) ofthe pressed surfaces were measured, and the accuracy of each die wasevaluated. The results are shown in Table 13.

                  TABLE 13                                                        ______________________________________                                        Results of Comparative Experiment                                                       Surface Surface condition                                                     roughness                                                                             after pressing                                                              before    10,000 30,000 40,000                                Sample                                                                              Type      pressing  times  times  times                                 No.   of die    (RMS,nm)  (RMS,nm)                                                                             (RMS,nm)                                                                             (RMS,nm)                              ______________________________________                                        249   Ni--W--P  1.04      1.13   2.06   Peeled                                250   Ni--Cu--B 1.02      1.09   1.87   Peeled                                251   Cu--Ti    1.05      1.12   2.07   Peeled                                252   Si--Zr    1.02      1.08   1.94   Peeled                                253   Ni--Mo    1.04      1.10   2.01   Peeled                                ______________________________________                                    

In the Sample Nos. 249 to 253, the molding dies did not have roughsurfaces,. and the films did not peel or crack even after press-molded30,000 times repeatedly. This shows the superior characteristicscompared to the conventional dies. However, the films peeled off fromthe base material when press-molded 40,000 times so that the process hadto be stopped then.

On the other hand, the dies in the Sample Nos. 254 to 273 of thisembodiment did not crack even after being press-molded 50,000 timesrepeatedly. The surface condition remained almost the same. The surfaceroughness hardly changed. This shows that these dies can press-moldglass having a high melting point, such as SK-12. Accordingly, bypress-molding glass by means of the dies for press-molding of thisinvention, it is possible to press-mold a large quantity of glassoptical elements having high melting points and shapes which wasdifficult to attain by a grinding process.

As a result, all the requirements which are necessary to directlypress-mold the above-mentioned glass optical elements with high accuracywere met. It enabled press-molding a large quantity of the glass opticalelements having high melting points and shapes which was impossibleprior to this invention.

Cemented carbide consisting mainly of WC was used as the base materialof the die for press-molding in this embodiment. It goes without sayingthat any other material can be used to attain the same results that hasheat resistance and sufficient strength to withstand the press-moldingprocess of optical glass. However, it is preferable to use cementedcarbide mainly consisting of WC, cermet mainly consisting of TiN or TiC,or WC sintered compact.

As for the intermediate layer, alloy films of Ni-W-P, Ni-Cu-B, Cu-Ti,SiZr, and Ni-Mo amorphous alloy film were used with cutting layers ofNi, SiC, TiN, and Ta₂ O₅. It goes without saying that the same resultscan be obtained by using the alloy films shown in the embodiments 1 to 5with cutting layers consisting of other metal, carbide, nitrogen, andoxide.

As far as the protective layer is concerned, Pt-Ir was used in thisembodiment, but the same results could be attained by using an alloyfilm of precious metal which includes at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W and Ta.

Furthermore, this embodiment referred to the manufacturing process of ahollow-shaped die with 1 mm radius of curvature. Shapes which aredifficult to attain with conventional grinding methods, such as dies fornon-axisymmetric lenses or microprism arrays, can also be processed withthis method.

What is claimed is:
 1. A method of press-molding glass optical elements,comprising press-molding glass, having a high melting point, at atemperature of 650° C. and higher using a die for press-molding glassoptical elements comprising:(a) a base material having heat resistanceand sufficient strength to withstand press-molding of optical glasselements; (b) at least one film on said base material comprising, analloy film containing P and one metal selected from the group consistingof Ni, Co, and Fe, and one metal selected from the group consisting ofSi, Ti, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, to form acutting layer; and (c) a surface protective layer on top of said cuttinglayer made of an alloy film comprising at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta.
 2. Amethod of press-molding glass optical elements as claimed in claim 1,wherein said die for press-molding glass optical elements furthercomprises an intermediate layer comprising at least one film having amaterial selected from the group consisting of metal, carbide, nitrideand oxide between said base material and said cutting layer.
 3. A methodof press-molding glass optical elements, comprising press-molding glass,having a high melting point, at a temperature of 650° C. and higherusing a die for press-molding glass optical elements comprising:(a) abase material having heat resistance and sufficient strength towithstand press-molding of optical glass elements; (b) at least one filmon said base material comprising an alloy film containing Cu and 20 to80 atom % of one metal selected from the group consisting of Ni, Co, Fe,Si, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, to form acutting layer; and (c) a surface protective layer on top of said cuttinglayer made of an alloy film comprising at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta.
 4. Amethod of press-molding glass optical elements as claimed in claim 3,wherein said die for press-molding glass optical elements furthercomprises an intermediate layer comprising at least one film having amaterial selected from the group consisting of metal carbide, nitrideand oxide between said base material and said cutting layer.
 5. A methodof press-molding glass optical elements, comprising press-molding glass,having a high melting point, at a temperature of 650° C. and higherusing a die for press-molding glass optical elements comprising:(a) abase material having heat resistance and sufficient strength towithstand press-molding of optical glass elements; (b) at least one filmon said base material comprising an alloy film containing Si and 20 to80 atom % of one metal selected from the group consisting of Ni, Co, Fe,Cu, Ti, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, and Ir, to form acutting layer; and (c) a surface protective layer on top of said cuttinglayer made of an alloy film comprising at least one metal selected fromthe group consisting of Pt, Pd, Ir, Rh, Os, Ru, Re, W, and Ta.
 6. Amethod of press-molding glass optical elements as claimed in claim 5,wherein said die for press-molding glass optical elements furthercomprises an intermediate layer comprising at least one film having amaterial selected from the group consisting of metal, carbide, nitrideand oxide between said base material and said cutting layer.